A wide variety of hand grip tools are known in the industry. Many of these tools are designed to do a specific operation while others are designed to do many operations through the use of changeable mating die halves. Such hand tools are generally either double action hand tools (DAHT) which have dies that close in an arc-like path or straight action hand tools (SAHT) which have straight line die movement.
A great many of these hand tools are of the type having a single stroke operation, i.e. having cooperating work members which are moved from a fully open position to a fully closed position during a single stroke of the handles. This type of arrangement does not provide much mechanical advantage, and consequently heavy duty tasks are difficult to perform. In an effort to make these tools easier to operate, the handles may be lengthened in order to increase the mechanical advantage of the tools. However, the lengthening of the handles creates a large handle span, preventing one hand operation and also eliminating the usefulness of the tools in a confined area.
In an attempt to provide some relief of the above problems multiple stroke hand tools have been developed which provide greater mechanical advantage than the single stroke tools. The mechanical advantage is provided through the use of a ratchet member driven by the movement of the handles as they are displaced toward each other. This mechanical advantage allows the handle of the hand tool to be positioned such that maximum grip strength of the operator corresponds with the maximum input force required for operation. As the diameter of the ratchet member is increased, the forces exerted on the drive means is decreased, allowing for a longer lasting hand tool. However, as the diameter of the ratchet member is increased, the overall dimensions of the tool must be increased resulting in a large, impractical tool. Another design feature of many of these multiple stroke hand tools is that no manual release means is provided. In other words, once the hand tool has begun to perform its operation, the operation must be completed, giving the operator no opportunity to manually override the hand tool. Consequently, if the operation is being performed improperly, the operator can do nothing to prevent it, resulting in wasted material and wasted effort. The few multiple stroke hand tools that have a manual release require that the manual release be engaged even when the operation has been completed; no automatic return is provided. This added step requires more time and effort to complete the operation.